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Task Review, 2005Rotorcraft Center of Excellence PS 1.2a Hybrid Active-Passive Rotor Systems for Vibration and Performance Edward Smith Professor Aerospace Engineering Tel : (814) 863-0966 Kon-Well Wang Diefenderfer Chaired Professor Mechanical Engineering Tel : (814) 865-2183 Principal Investigators Graduate Student Jun-Sik Kim 2005 RCOE Program Review May 2, 2005

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Task Review, 2005Rotorcraft Center of Excellence Background vibrationThe rotorcraft industry is aggressively pursuing successful and cost effective active control systems to reduce vibration. Blade loadsBlade loads are design constraints for primary control and life cycle. Actuator authorityActuator authority present major technical barrier.

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Task Review, 2005Rotorcraft Center of Excellence Problem Statement and Task Objective Design high authority actuator system Large stroke and force and low electric power Design high authority actuator system Large stroke and force and low electric power hybrid design approach Penn State (1996 - ) improved actuators UMd, PSU, et al. V gs V w/ control w/Control fs w/ control w/Control Vibration Blade loads Design active controller together with passive parameters Re-configuration of passive structure (m, GJ, EI, etc) Design active controller together with passive parameters Re-configuration of passive structure (m, GJ, EI, etc) Objective: To address the critical issues and advance the state- of-the-art of rotor vibration suppression and blade loads reduction through combining the two approaches High authority PZT actuators Effective hybrid vibration/blade loads control system How do we design effective active vibration/blade loads control systems for future rotorcraft ?

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Task Review, 2005Rotorcraft Center of Excellence Piezoelectric Actuator Scaling Aerodynamic Moment and Block Torque non- dimensionalized with small scale values H aero * ~ c 2 R T* ~ c 3 Performance as Blade Size 0 100 200 300 400 500 600 0510152025 Chord (in) H aero * T* Small scale blade chord MD900 blade chord 3 51 1 7 3 H aero * T*

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Task Review, 2005Rotorcraft Center of Excellence Boeing 2xFrame Actuator 2003 Full Scale Whirl Test Results (SPIE 2004, Straub et. al) Large rotor test stand (LRTS) Modified MD 900 bearingless rotor 3~3.5 degrees in hover (450V) Flap deflection vs. rotor speed multiple

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Task Review, 2005Rotorcraft Center of Excellence 1) High active authority 1) High active authority and low electric power of actuator for actuator/flap coupled systems Resonant Actuation System (RAS) 2) Multiple trailing edge resonance actuation system 2) Multiple trailing edge flap configuration to utilize the resonance actuation system Vibration and blade loads reductions Technical Barriers and Solution Idea Resonance Actuation System(RAS) Multiple Trailing Edge Flaps

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Task Review, 2005Rotorcraft Center of Excellence Technical Evolution Natures Flight Actuators

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Task Review, 2005Rotorcraft Center of Excellence Summary of 2001 - 2003 Accomplishments Aeroelastic flap/torsion model for composite rotor blade was developed (code validation, 2001) Refine control algorithm of hybrid design was developed to achieve both blade loads and vibration reductions with minimum control efforts (2002) Multiple trailing edge flap configurations with RAS was explored to reduce the vibration (2003) Blade loads and vibration control via TEF Circuit with negative capacitor and active inductor/blocking filters was explored to reduce electric power (2001) New concept to enhance the active authority of PZT actuators was developed and evaluated on PZT benders, stacks, and tubes (2002) Full-Scale PZT tube / R-L-C circuit system was experimentally realized and evaluated (2003) Active authority enhancement of PZT actuator

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Task Review, 2005Rotorcraft Center of Excellence 2004 Review Team Comments The task made good progress and made good responses to the last year suggestions. The task deals with vibration only and it is suggested to check noise aspect of the concepts. - Other Research is focused on trailing edge flaps for noise reduction. (e.g. Prof. Friedmann at Univ. of Michigan has 2005 AIAA and AHS papers on this subject). - Researchers in industry (e.g. Straub et al) have also examined this idea. - A thorough investigation of noise reduction was considered beyond the scope of the present investigation. The review team is curious about drag penalty of TEF? - This is an important question. - Increments in section drag are modeled in the airload calculation - Primary penalties are for flap deflections near transonic Mach number (adv side) and negative deflections at high angles of attack (retreating side) - Proper control law design can mitigate these penalties (Zhang, Smith, Wang, 2000)

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Task Review, 2005Rotorcraft Center of Excellence Retrofit Design at 0.30 Retrofit Design at 0.15 Performance Enhancement Large flap deflections may occur around 90 and 270 azimuths, which can cause aerodynamic penalties - stall and separation Flap Up Flap Down

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Task Review, 2005Rotorcraft Center of Excellence Modified objective function and control algorithm : The active flap deflections at certain time history : Weighting factor Performance Enhancement

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Task Review, 2005Rotorcraft Center of Excellence Retrofit design at advance ratio of 0.30 Active Flap deflections around 270 azimuth are reduced to within 2 degrees Retrofit Retrofit with constraints Performance Enhancement

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Task Review, 2005Rotorcraft Center of Excellence Hybrid design at advance ratio of 0.15 Active flap deflections around 90 azimuth are reduced from more than 6 degrees to about 2 degrees Hybrid Hybrid with constraints Performance Enhancement

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Task Review, 2005Rotorcraft Center of Excellence Summary of Accomplishments in 04/05 Analysis and Experiment of Piezoelectric Resonant Actuation Systems Analysis is performed to explore the feasibility of a resonant actuation system (RAS) Dynamic characteristics of a RAS is examined via perturbation method (forward flight) Power consumption of a RAS is explored Experiment of a RAS with adaptive feed-forward controllers Bench Top Test A voltage signal function is derived from the analytical model and implemented using Matlab/dSPACE A phase controller, so called phaser, is implemented to track the phase variation near a resonant frequency Actuator amplification mechanism of a RAS is modified to improve the dynamic performance 6.0 degrees are achieved

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Task Review, 2005Rotorcraft Center of Excellence IDEA Actuator authority enhancement 1.Resonance can be utilized to improve the actuator authority Resonance Actuation System Baseline - Small active authority over operating range Increase authority Increase authority via mechanical tuning and electrical tailoring May not cover the entire range of operating frequencies 3,4,5/rev 3/rev 4/rev 5/rev Frequency, Hz Typical Trailing Edge Flap Deflections Required authority Single nominal actuator (baseline) 2.Electric network can help to broaden and flatten the resonant driver effect 3/rev 4/rev 5/rev Three Small Actuators Three small flaps Single flap Three small flaps Tune to Operating Frequency via Mechanical Tuning frequency Actuator stroke Broaden and Flatten via Circuit design

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Task Review, 2005Rotorcraft Center of Excellence Multiple TEF w/ RAS Resonance Actuation System 1) PZT Actuator 2) Trailing Edge Flap (Aerodynamics) 3) Electric Circuit Resonance Actuation System 1) PZT Actuator 2) Trailing Edge Flap (Aerodynamics) 3) Electric Circuit Inductor: tune to operating frequency (e.g., 3,4,5/rev) Resistor: flatten the resonant peak Negative capacitor: broaden the resonant driver effect Inductor: tune to operating frequency (e.g., 3,4,5/rev) Resistor: flatten the resonant peak Negative capacitor: broaden the resonant driver effect RAS Electric Network Amplification mechanism Mass moment of inertia of TEF Amplification mechanism Mass moment of inertia of TEF Mechanical Tuning Resonance Actuation System Application

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Task Review, 2005Rotorcraft Center of Excellence Mechanical Tuning Resonant frequency : 2 = K / M Tuned to the operating frequency (e.g. 3, 4, 5/rev) Tuning parameterTuning massAmplification ratio Tuning parameter: Tuning mass, Amplification ratio Tube actuator: K p,M p Amplification mechanism, = A m A m Amplification mechanism, = A m , A m = l lever / l offset (e.g. A m =5 will provide 5:1 amplification) Trailing-Edge Flap: M f Aerodynamic loads: K f Tuning mass: M tune MK Flap hinge Hover: stiffness is constant Forward flight: stiffness is varying along the azimuth Periodic coefficient due to 1/rev aerodynamic forces Time-varying characteristics of actuation system will be discussed further Hover Forward Flight

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Task Review, 2005Rotorcraft Center of Excellence Actuator authority enhancement at tuned frequency via Mechanical tuning Problem: It is hard to control Active authority: The circuit can broaden and flatten the resonant effect of the tuned system and still maintain high authority Inductor: tune to operating frequency (e.g., 3/rev, 4/rev, 5/rev) Negative capacitor: broaden the resonant driver effect Resistor: flatten the frequency response around the resonant peak Electrical Tailoring frequency Actuator stroke Broaden and Flatten via Circuit design Bruneau et al.(1999) Tang and Wang (2001) Behrens et al. (2001). (Resistor, Inductor) Resonant frequency Operating frequency: 3,4,5/rev Phase variation near resonant freq. Need to design controller to track phase variation Developed and tested in this years effort Phase variation near resonant freq. Need to design controller to track phase variation Developed and tested in this years effort Phase plot

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Task Review, 2005Rotorcraft Center of Excellence Perturbation Method in Forward Flight Primary resonance at = (resonant frequency in hover) Resonances due to time-varying characteristics at 2 = 2, ( 1) 2, ( 2) 2 Flap response q t includes other harmonics: ( 1), ( 2), For example, if =4, then q t includes 2,3,4,5,6/rev harmonics Time-varying characteristics of actuation system Equations of motion of a coupled system w/o circuitry Normalized equations for the purpose of perturbation Perturbed solution up to 2 : Theodorsens theory for trailing edge flap

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Task Review, 2005Rotorcraft Center of Excellence Influence of advance ratios to the major resonant frequency is not significant RAS can be applied to forward flight as well as hover Actuation system w/o circuitry Frequency Responses in Forward Flight Actuation system with circuitry RAS in hover The actuator authority is significantly increased from 1.25 degree to 4.5 degree Flat and wide shape near the resonant frequency (approximately 8 Hz). RAS in forward flight Main characteristics of the RAS (high authority with wide bandwidth) are achieved in forward flight Operating frequency, 4/rev, 26.6Hz Hover Advance ratio 0.35 Advance ratio 0.15

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Task Review, 2005Rotorcraft Center of Excellence Flap Time Histories in Forward Flight ( =0.35) 4/rev voltage signal input 4/rev harmonic component is increased from 1.5 to 3 degrees Need to develop controller to resolve the side effects Nominal actuation system Resonant Actuation System

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Task Review, 2005Rotorcraft Center of Excellence Summary of Accomplishments in 04/05 Analysis and Experiment of Piezoelectric Resonant Actuation Systems Analysis is performed to explore the feasibility of a resonant actuation system (RAS) Dynamic characteristics of a RAS is examined via perturbation method (forward flight) Power consumption of a RAS is explored Experiment of a RAS with adaptive feed-forward controllers Bench Top Test A voltage signal function is derived from the analytical model and implemented using Matlab/dSPACE A phase controller, so called phaser, is implemented to track the phase variation near a resonant frequency Actuator amplification mechanism of a RAS is modified to improve the dynamic performance 6.0 degrees are achieved

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Task Review, 2005Rotorcraft Center of Excellence Feed-Forward Controller for RAS Electric network is realized via Voltage Signal Function which is derived from the coupled piezoelectric equations The phase angle is adaptively corrected through the feedback of the output signal Electric network is realized via Voltage Signal Function which is derived from the coupled piezoelectric equations The phase angle is adaptively corrected through the feedback of the output signal Adaptive phaser to track the phase variation Voltage Signal Function emulating of electric network Phase plot

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Task Review, 2005Rotorcraft Center of Excellence Experiment Set-up 8 inch PZT tube, 12 inch flap (inertia only) Amplification ratio: 5 (current), 15 (future) Mechanical tuning to 4/rev (26.6Hz) 8 inch PZT tube, 12 inch flap (inertia only) Amplification ratio: 5 (current), 15 (future) Mechanical tuning to 4/rev (26.6Hz)

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Task Review, 2005Rotorcraft Center of Excellence Bench Top Test Results Actuator authority at the tuned frequency (26.6Hz) Increases about 3.5 times when compared to the static deflection (which would be produced by nominal actuation system) with 8 Hz bandwidth The phase near a resonant frequency varies Implemented adaptive controller is able to accurately follow the reference Frequency Response Phase Control at 24 Hz Operating frequency w/ voltage signal function w/o voltage signal function 3.5

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Task Review, 2005Rotorcraft Center of Excellence Demonstration of RAS Full-scaled PZT tube actuator fabricated (Jose Palacios and Edward Smith, 2005) PZT tube is 4 inches long Simulated aerodynamic loads Two springs (80 lb/in total) Applied voltage: 2250 Volts Mechanical tuning: 33.3 Hz for MD 900, 5/rev Flap deflections with simulated aerodynamic loads 12 inches flap, 400 RPM 6.0 degrees are achieved at the operating frequency Nominal actuation authority is 0.2 degrees: 30 times increases Mechanically tuned actuator w/o voltage signal function Test with voltage signal function is scheduled in near future Resonant Actuation System with simulated aerodynamic loads & improved amplification mechanism

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Task Review, 2005Rotorcraft Center of Excellence Planned Efforts in 2005 Controller design for flap responses in forward flight Reduce the side effects due to time-varying characteristics Investigate the characteristics of a RAS further Continue the test of a RAS with a voltage signal function Nonlinear characteristics of a RAS Controller design for flap responses in forward flight Reduce the side effects due to time-varying characteristics Investigate the characteristics of a RAS further Continue the test of a RAS with a voltage signal function Nonlinear characteristics of a RAS Controller for side effects Characteristics of a RAS

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Task Review, 2005Rotorcraft Center of Excellence Summary of Overall Accomplishments 1.Development of actuation systems for active flap rotors A resonant actuation system (RAS) was developed Bench top testing of full-scaled actuation system Dynamic characteristics of a RAS in forward flight were explored Actuator amplification mechanism of a RAS is modified to improve the dynamic performance Objective: To advance the state-of-the-art of rotor vibration suppression and blade loads reduction through combining the two approaches 2.Development of analytical tool for rotor analysis Free-wake for main rotor, unsteady aero and finite wing effects for flaps Active load controls via dual flap (blade loads reduction) Vibration reduction via multiple trailing edge flaps controlled by resonant actuation system 1. High authority PZT actuators 2. Effective vibration/blade loads control system

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Task Review, 2005Rotorcraft Center of Excellence Future Work Hover or wind tunnel test of a RAS Active load controls for Heavy Lift Helicopters Dual flap configuration together with RAS for light weight rotors Damage detection using active flaps in forward flight Active interrogation could be combined with active loads control Hover or wind tunnel test of a RAS Active load controls for Heavy Lift Helicopters Dual flap configuration together with RAS for light weight rotors Damage detection using active flaps in forward flight Active interrogation could be combined with active loads control Damage identification using trailing edge flaps 2. Straightened blade Active load controls via dual-flap 1. Deformed blade

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Task Review, 2005Rotorcraft Center of Excellence External Interactions, Leveraging and Technology Transfer Have had discussions with US Army AFDD (Mark Fulton, smart rotor testing, resonant actuator and circuit concept, flap aspect ratio effect) Boeing (Friedrich Straub, actuator requirements) Sikorsky: visited (A. Bernhard, feasibility of multiple-flap configuration) U. Maryland (I. Chopra et. al, hinge moments) U. Michigan (P.P. Friedmann, auto-weight control)

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Task Review, 2005Rotorcraft Center of Excellence Novel, high authority flap actuation concepts using single crystal stacks SBIR (Small Business Innovation Research) Invercon and PennState Buckling beam actuator together with RAS high actuation authority Novel, high authority flap actuation concepts using single crystal stacks SBIR (Small Business Innovation Research) Invercon and PennState Buckling beam actuator together with RAS high actuation authority External Interactions, Leveraging and Technology Transfer

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Task Review, 2005Rotorcraft Center of Excellence Publications and Presentations 1.Jun-Sik Kim, Edward C. Smith and Kon-Well Wang, "Active loads control of composite rotor blade via trailing edge flaps", 44th AIAA/ASME/ASCE/AHS/ASC SDM Conference, Norfolk, Virginia, April 7-10, 2003. 2.Jun-Sik Kim, Kon-Well Wang and Edward C. Smith, "Active authority enhancement of piezoelectric actuator design via mechanical resonance and electrical tailoring", Fifth International Conference on Intelligent Materials (ICIM) June 14 - 17, 2003, State College, Pennsylvania 3.Jun-Sik Kim, Edward C. Smith and Kon-Well Wang, "Helicopter Vibration Suppression via Multiple Trailing Edge Flaps Controlled by Resonance Actuation System", Tenth International Workshop on Dynamics and Aeroelastic Stability Modeling of Rotorcraft System, November 3-5, 2003, Student Success Center, Georgia Institute of Technology, Atlanta, GA. 4.Jun-Sik Kim, Kon-Well Wang and Edward C. Smith, High Authority Piezoelectric Actuator Synthesis through Mechanical Resonance and Electrical Tailoring, Adaptive Structures and Material Systems Symposium, The Winter Annual Meeting of the ASME, November 16 - 21, 2003, Washington Marriott Wardman Park, Washington DC 5.Jun-Sik Kim, Edward C. Smith and Kon-Well Wang, Helicopter Vibration Suppression via Multiple Trailing Edge Flaps Controlled by Resonance Actuation System, the AHS 60 th Annual Forum, Baltimore, MD, June 7- 10, 2004. 6.Jun-Sik Kim, Kon-Well Wang and Edward C. Smith, High Authority Piezoelectric Actuator Synthesis through Mechanical Resonance and Electrical Tailoring, Journal of Intelligent Material Systems and Structures, Vol. 16, No. 1, pp. 21-3, 2005 7.Jun-Sik Kim, Kon-Well Wang and Edward C. Smith, Development of a Resonant Actuation System for Active Flap Rotors, the AHS 61 st Annual Forum Gaylord Texas Resort, TX, June 1-3, 2005. 8.Jun-Sik Kim, Kon-Well Wang and Edward C. Smith, Design and Analysis of Piezoelectric Transducer Based Resonant Actuation Systems, Adaptive Structures and Material Systems Symposium, The Winter Annual Meeting of the ASME, November 6-11, 2005, The Walt Disney World Swan & Dolphin Hotel, Orlando, Florida

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Task Review, 2005Rotorcraft Center of Excellence Tasks 20012002 2004 2005 Extension of hybrid analysis to composite rotors, and actuator- circuit model Initial studies on composite rotor and actuators with APPNs Refinement for unsteady aero and control algorithm(dual flap) New actuator concept development and integrated study with rotor Refine aerodynamic model Design, fabrication of actuators Methodology for robust design and adaptive control Refinement and testing of resonance actuation system Development of controller for flap responses in forward flight and investigation of nonlinear features of a RAS 2003 Near Term Mid Term Long Term Schedule and Milestones

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Task Review, 2005Rotorcraft Center of Excellence Questions? The End

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Task Review, 2005Rotorcraft Center of Excellence Appendix

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Task Review, 2005Rotorcraft Center of Excellence Influence of advance ratios to the major resonant frequency Not significant Averaged frequencies along the azimuth Almost constant with respect to the advance ratio RAS can be applied to forward flight as well as hover Actuation system w/o circuitry Frequency Responses in Forward Flight Instantaneous frequencies Operating frequency, 4/rev, 26.6Hz Hover Advance ratio 0.35 Advance ratio 0.15